Automatic cable tester or fault analyzer means



4 Sheets-Sheet l TTT l.. .1. KABELL ET A1.

AUTOMATIC CABLE TESTER OR FAULT ANALYZER MEANS Filed sept. 2e, 195o x6; Herma/H x/ sxvvga 30103735 7H/M 01 Dec. 16, l 952 W/ TNESSES. fw' c'. WM

Dec. 16, 1952 .1. KABELL ET A1. 2,622,130

v AUTOMATIC CABLE TESTER 0R FAULT ANALYZER MEANS nv O IN VEN TORS.' W/TNESSES' ALLEN L. DYER LOU/5 J KBELL QM L W2 AND R/GHARD A. I/OHAI?D,S`

32ML? Mm Dec. 16, 1952 1 KABELL ET AL I 2,622,130

AUTOMATIC CABLE TESTER OR FAULT ANALYZER MEANS Qq/gif Mx Dec. 16, 1952 J. KABELI. ETAL 2,622,130

AUTOMATIC CABLE TESTER OR FAULT ANALYZER MEANS Filed sept. 2e, 195o 4 sheets-sheet 4 IN VEN TORS.' Z ALLEN L. DYER LOU/.S` J KABELL v am m AND R/OHARD A. R/GHAE'DS Patented Dec. 16, 1952 AUTOMATIC CABLE TESTER OR FAULT ANALYZER MEANS Louis J. Kabel1, Richard A. Richards, and Allen L. Dyer, Albuquerque, N. Mex., assignors to the United States of America as represented by the United States Atomic Energy Commission Application September 26, 1950, Serial No. 186,848

(Cl. F75-#183) 6 Claims.

The present invention relates to an automatic apparatus for testing or analyzing for faults, a cable having a plurality of wires. The particular characteristics or faults which the apparatus is intended to test or analyze for are conductive integrity of each wire including its end connectors and the insulation resistance between each wire and the remaining wires in the cable which are tied together and grounded. The tester operates to identify any wire having a fault either because of excessive resistance or insulation leakage. The apparatus could, of course, conceivably be set up to indicate other types of faults in the same manner.

The apparatus embodies means so that the wire in which a fault is encountered is indicated on a dial by number and the type of fault is indicated by an indicator or signal lamp.

In many types of modern equipment, particularly for use in aircraft and the like, Various types of electrical and other equipment are employed -Wherein the wiring requires the use of large numbers of cables, each having a substantial number of wires. In order to insure the proper operation of equipment and to insure against faults cr defects in the cables which would render the equipment ineffective or inoperative it is essential that the individual wires in each cable be checked, that is, tested for faults. When this is done manually by individually testing each Wire with appropriate instruments the operation is, of course, a tedious and time-consuming process and, of course, involves the risk that one or more individual wires may be missed in the testing operations. It is, accordingly, an object of the present invention to provide an automatic testing apparatus whereby cables having a plurality of Wires 'may be automatically tested or analyzed for faults as described above simply by plugging the cable into an adaptor associated with the tester and placing the tester in operation.

Another object of the invention is to provide a cable tester having characteristics as outlined in the foregoing wherein an automatic stepping relay is provided, controlled by a cycling timer, the stepping relay being operatively connected to a plurality of sequentially operated relays which are wired to an adaptor unit into which the ends of a multiple wire cable may be plugged in such a manner that each of the sequentially operated relays is operable to connect an individual wire to a testing device controlled by the cycling timer which analyzes the individual wire for faults by connecting a high voltage source to one end of the wire to check for insulation resistance and then connecting a low voltage source between the ends of the wire to check for continuity.

The system as outlined in the foregoing object may include a signalling device operable to interrupt the operation of the stepping relay and to provide a signal in the event that a fault is encountered in an individual Wire.

As pointed out above the tester embodies a cabinet and there is also provided an adaptor unit which fits into a suitable recess inv the cabinet, the purpose of the adaptor unit being to adapt the tester for testing various different types of cables having diiierent numbers of Wires and having different types of plugs, having varying numbers of connector pins in different geometric patterns. The tester cabinet has within the recess a pair of rectangular contact panels each having a plurality of contacts and the adaptor unit has a pair of similar panels with contacts which engage with the contacts of the cabinet panel when the adaptor unit lis in place. The adaptor unit has a front panel carrying a plurality of receptacles adapted to receive plugs at the ends of a cable to be tested and these receptacles may be such as to receive any number and type of plugs asdescribed above. The adaptor unit also carries a selector switch which is wired into the system so that after the last Wire in a particular cable has been checked, regardless of the number of wires, the system will recycle and reset itself back to the starting point.

In accordance with the above itis another object of the invention to provide an adaptor unit including a selector switch as set forth in the foregoing.

Further objects and numerous advantages yof the invention will become apparent from the following detailed description and annexed drawings, Figure l of which is a partial circuit diagram of a preferred form of the invention, showing mainly the stepping relay.

Figure 2 is another portion of the wiring diagram of Figure 1.

Figure 3 is a further portion of the wiring diagram of Figure 1.

Figure 4 is a schematic diagram illustrating the principle of the adaptor unit and the cable selector switch.

The entire apparatus of the invention Vis contained within a suitable cabinet having a front panel with the signal devices and rindicators mounted thereon. The cable vto be tested is plugged into appropriate receptacles in 'the adaptor unit which fits into the cabinet and the test is begun by pushing a start button. The test then proceeds automatically from wire to wire.

After the start button is pressed a cycling timer takes control of a stepping relay which operates step by step to seouentially energize a group of relays, each Vof which is associated with an individual wire of the cable to be tested. Upon energization of each of the sequentially operated relays, the cycling timer energizes a change-over relay which momentarily connects the two sources of voltage in the manner described above to the individual wire to test that particular wire; When the next of the sequentially operated'relays is energized the cycling timer causesl ythe sametests to be performed on its associated wire.

In the event that a fault is encountered the automatic operation stops and one of the signalling devices indicates the fault and the 'start but-` ton must be again pressed to restart the apparatus.

The system of` the `invention may be said to be built aroundfa-stepping relay (Fig. 1) which is-a spring acting type of mechanism which automatically steps fromI one-contact to another. Therelay-of the present invention has contacts numbered 'from l to --39 Vas show-non Figure l and andnitial or home positioncontact as indicated at H. The relay itself is-designated by the numeral 4I and ithas an armature `l2 and a winding 43, thew connectionsv between the armature and the contactor mechanism embodying a ratchet 'such that af-ter vthe windinghas lbeen energized by a pulse-of current, upon deenergizationthe relay steps-to1the -next contact. The ratchet 'mechanism actuates a double wiper arm' asshown. The relay-'M -also embodies a switch bladell'tcooperating fWith-acontact Yl5 which is closed when the relay is' dei-energized. Y

The relay 4l during operation 'is controlled by a fcyclingftimerlFig. 2) designatedgenerally as 48, this timer comprising atiming motor 49 which drives ca/ins 5l), 5|.v and 52. These' cams operate switches'53; 54 and'55respectively.- The motor 49 drives its shaft at a speed of one revolution per second so'that the time cycle'of the cam loperatedfswitches is one cycle per second.` The sequence or switch Voperations is such that the switch flfisf normally closed, the purpose of this switch being for starting synchronization as will bev-described andr` this switch is open from .15 secondto .25`second Yduring the cycle 1to begin the operation. Switch Y55'closes for .lsecond after switch 54fhas. opened andV this switch, that is,

Aswitch i551 provides a pulsefor stepping the relay 4l. The switch-53 is closed from .'30 to .65 second during the cycle to provide changeover from one test to -the other.

Starting of -a test is controlled by a manual starting switch e (Fig. 2) which is a push button switch closedby depressing the switch. Switch 5'5-'controlsr a relay A having the usual winding and armature andblades All, A2 andAS cooper- ,atingwith contacts alg-a2, a3 and all.-

The system includes a number of 'similar relays as designated at B, C, D, E, Fand G, these relays having switch blades and contacts designated by a corresponding system of alphabeticalY characters. The `operation. of these relays will be referred to more in detail presently.

Therelay B is designated as the home position hold-ofirelay and it is energized when'the relay 4 I -is-in` home position.

The-relay'E is designated as the homing relay and itbecomesfenergized after the lastwire'in the cable has been checked and it causes the system to recycle to home position. Relay E may be manually energized by switch 5l for manual recycling as will be described.

The system also includes a number of wire selector relaysVV (Fig. 3) eachof which acts-to connect an individual wirefor testing and these relays are designated EK, 2K, 3K, etc. there being one relay for each of the contacts of relay lll these relays having switch blades and contacts designated by a corresponding system of alphabeticalcharacters.

The characters J.| and J 2 (Fig. 3) designate a pair of contact panels in the tester cabinet as Vreferredtol abovateach having a plurality of contacts, forrinst'ancatz. The first contact of each of .these panels isconnected to one of the switch bla'des'Kland K2'respectively of relay IK. Subsequent contacts of these panels are similarly connected to the relays 2K, 3K, and so on. As pointed outv in the .foregoing the adaptor` unit whichwill be referred toA againpresentlyhas contact panels which engage. with the .panels J I. and J2 vvhenltheadaptor 4unitis-in place.

The power supply for the system (Fig. 2) .is designated at 55 andthereis included' atransformer 59 having a primary 69,a'6-3vo1t secondary 6i, a center tap 220 volt secondaryfwinding, anda volt secondary winding 63.

The power supply for. the Windingll :of relay 4l (Fig. l) includes apair of'Thyratron rectifier tubes Vl and V2 having a cathoderplateVgricl andV screen grid-as shown and cathode heaters which are connected in parallel across the 6.3 volt winding El as shown. The plates of tubes VI and V2 areconnectedacross the 220 lvolt Winding 62 as shown. The cathodes oiV the ltubes Vi Aand V2 are connected together and to one: end ofthe winding Sby avwire65 as-shown andalso tothe center tap of the A6.3l V. winding 5l. The tubes V1 andVZ operate-in the-.usual ina-nner to provide rectied currentfor operation-.of the relay el.Y

Numeral .61 (Fig. `2) designates a hig-h voltage power. supplyof 500volts, forexample, connected with the-power supplyflines 58, for purposes of making .the insulation test.

Therelay M-is a sensitive type of relay which is apart of the insulation testing circuit' and thisv relay hasa winding''which becomes energized if Vthealeakage currentvfrom the wire Ybeing tested .becomeshgh enough. Relay M is of a type havinga second winding l0 and armature and if windingv abecomes energized-the relay must be. reset by energization of winding l0. Relay Mhas a switchblade-Ml and cooperating contact ml.

As previously described the adaptor unit rlts into a recess `in ythe cabinet-ofthe testerY and has contact panelsl which engage withthe panels J i and J2. inthe tester cabinet. On Figure 4 the corresponding contact panels of the adaptor unit are designated as J 3 and J il. Figure 4 iseu wiring diagram .illustrating the principle involved in the wiring: between ,the contact panelsJS and J 4 and the various receptacles on the panel of the adaptor unit and the selector switch designated as i3. The selector switch i3 is a rotary type switch having a wiper arm l@ which cooperates with a plurality of contacts "i5, 75, and 77, contact 'l5 beingfthe oil position contact. The'adaptor unit nascorrespondi-ng receptacles J5 and J6 -as shown and it mayV have a plurality ofsimilar sets of receptacles adapting it for testing as many differentrcables. The drawing lis'merely illustrative in this-respect:

Aswill be explained presently the various contacts of the selector switch 13 are'wired to the receptacles on the right hand side in such a way that the system will reset after a pre-determined number of wires has been checked, that is, as will be observed presently if the selector switch 13 is set to its contact 16, for example, the system will reset after two wires have been checked; if it is set to its contact 11 it will reset after seven wires have been checked and so on.

' To start operation of a test after a cable has been plugged into the adaptor unit the start switch 56 is depressed which energizes relay A by connecting its winding directly across the 110 volt secondary winding 63 of transformer 59. When relay A is energized it establishes a locking circuit for itself across the winding 63 and through the cam switch 54, via contact al, blade Al, cam switch 54 and thence back to the other side of transformer secondary coil 63. Upon the establishment of this locking circuit the start button 56 ,can be released, and the locking circuit will continue to hold blade AI in closed position. The operation does not begin until cam has been rotated by the timing motor 49 to a position to open switch 54 which interrupts the locking circuit for relay A de-energizing this relay. Upon energization of relay A its blade A2 closed against contact a2 and connects winding 43 of relay 4| to the 110 volt D. C. power supply which causes this relay to energize and to thereby -prepare it for stepping operation. The spring-actuated ratchet mechanism of this relay is such that it steps to its first contact No. 1 upon de-energization of winding 43. The circuit for the winding 43 is from the center tap of transformer secondary winding 62 through wire 85, wire 86, contact a2, blade A2, wire 81, winding 43, wire 65, the rectifier tubes V| and V2, back to the winding 62. When relay A de-energizes as a result of opening of switch 54 by cam 5| its contact a3 closes with blade A2 and this prepares a circuit for providing electrical pulses for energizing winding 43 of relay 4| for sequentially stepping this relay to its various positions. This stepping pulse circuit is controlled by cam switch 55, operated by cam '52, and, as will be observed, operation of this switch is synchronized with switch 54 so that the stepping operation does not begin until after cam switch 54 has de-energized relay A. The stepping pulse circuit whereby the relay 4| steps to its various positions will be described presently.

y Upon operation of the above described starting synchronization circuit whereby winding 43 was energized and deenergized the relay 4| steps to its number l position and through wire 90, which connects with the contact at this number l position, relay iK now becomes energized by having its winding connected across the 110 volt winding 63. This circuit from the winding of relay IK is through the contact fl and blade FI of relay F by way of wire 89, wire 94, and wire 93; relay F is in the cle-energized position at this time. Contacts 76| and 7c3 of relay IK are connected, respectively, to the poles or blades G2 and GI of relay G by wires 9| and 92, respectively, so that when relay IK is energized and poles KI and K2 are closed against contacts kl and k3, respectively, the ends of the first wire to be tested are connected to the poles G2 and Gl of relay G as will be observed. When relay |K is de-energized one end of theirst wire to be tested is connected .t'o vground through resistor 99 and .the

6 other end of the first wire to betested is con-,-` nected to ground through a resistor |02.

The cycle now continues and the next step in the cycle is the closing of cam switch 53 by cam 50, which energizes relay G for setting up circuits for performing the test as to the leakage resistance of the wire being tested. The circuit for the winding of relay G is from the volt Winding 63 through wire 93, wire 94, wire 95, coil of relay G, wire 96, cam switch 53, wire 91, blade B2 and contact b2 of relay B and wire 98, back-'to winding 63. When relay G is thus energized its contacts gl and g3 are in closed relationship with blades G2 and GI and connect both ends of the' wire being tested to wire |00 which connects to the 500 volt supply 61 which is in turn connected to the winding 69 of relay M. If the leakage vcurr rent from the wire being tested becomes high enough winding 69 energizes causing closure of blade M| against contact ml, which thereby establishes a circuit that energizes relay D by connecting its winding across'the 110 volt winding 63 (via wire 93, wire 94, blade MI, contact rml, coil of relay D, and the return wires back to the other end of the transforming coil 63). With leakage current energizing relay D, blade D2 is closed against contact d2. Contact d2 of relay D now energizes a signal lamp |0| indicating a fault in that the leakage resistance of the wire being tested is insuicient. (Opening of contact dl upon energization of relay D interrupts the stepping pulse circuit and prevents continued stepping operation of relay 4| as will be described presently.)

When cam switch 53 opens, in response to rotation of cam 50, relay G is de-energized and its contacts g2 and g4 contact blades G2 and G| so as to now connect the ends of the wire being tested to the resistor |03, a portion of which is in shunt with the winding of relay C, 'and to the 6.3 volt winding 6| respectively. This circuit extends from blade GI through contact g2, resistor |03, sliding contact |06, coil of relay C, wire |64, wire |65, transformer coil 6|, wire |36, and contact g4. Blades Gl and G2 connect with wires 9| and 92 that join with contacts k3 and kl, respectively, with which the test wire connects by blades K2 and K This circuit constitutes the continuity checking circuit. Resistor |63 has a sliding contact |06 providing a means of adjusting the current in the winding of relay C so that it will not energize when a continuity current of less that two amperes ows. If there is lack of continuity as established in this manner relai7V C will fail to energize causing engagement of its blade C| and contact cl which lights an indicator lamp |01 indicating lack of continuity. During the testing of individual wires the relay C' will periodically energize and de-energize causing flashing of the lamp |61 but this does not indicate a fault; only the fact of lamp |01 coming on, and remaining on, indicates lack of continuity. The stepping pulse circuit extends through the contact c2 of relay C and it becomes interrupted upon deenergization of relay C indieating a fault. Thus it will be observed that if either the leakage resistance or continuity checks are negative the stepping pulse circuit is interrupted and continuation of the test is prevented until there has been manual intervention.

The stepping pulse circuit whereby the relay 4| automatically steps from contact to contact for checking individual wires is controlled bythe cam switch 55 as pointed out above and this circuitis as follows: from the center .tap of winding ,7 S-ZthI'u'ghwire'85,.wire 98, contact b2 of relay B, blade B2,'wirev9'|, wire ||0, blade CI and contactcZof relay C,'wire II I, contact dI and blade DI. of. relay D, wire |92, cam switch 55, wire IIS, contactv e3 and -blade E2 ofv relay E, wire I I4, contact a3 and bladeAZ of relay A, wire, winding 43of relay 4|, wire 65 and through the rectifier tube'sback to the .winding 92. It will be observed thatconnected across the various control contacts 'of the. above vdescribed stepping pulse circuit isfa series connected' condenser II'I and resistor H8, the purpose of which is to'reduce arcing across the contacts of switch 55 and contacts a2 and A2 of relay Aand contacts 44 and 45 ofrelay 4I.. From. the foregoing it will be observed that successive closures ofthe cam switch 55 energize.: the relay 4| in pulses. causing it to step successively from one contact to another andat eachcontact a corresponding one of the relays IK, 2K, etc. becomes energized. Should the stcpping. pulse' circuit become interrupted as a result ofacheck on one of the wires being tested being negative an appropriate indicator lamp cornes on as described.r

In the event of a negative insulation resistance test causing energization of winding 69 of relay M this relay locks up and must be reset by energization of winding 10. This will come about as a result of the operators restarting the test by again depressing the push button 59 to energize the relay A; contact a4 of relay A will connect winding- 'i0 across the 110 volt winding E3 and this will reset the relay M.

The relay 4| includes a dial on the front panel of the tester cabinet and this dial is indexed to indicate the number of the defective wire in the cable in the event of a negative check. The number of the wire will be indicated since the relay will stop opposite this number on the dial.

After the last wire in the cable has been checked and found satisfactory the relay 4| will step to its next position and before relay G becomes energized the winding of relay E' will be connected across the 6.3 volt winding 6| to energize this relay. This circuit will be through the cable selector switch '|3 forming part of the adaptor unit as shown on Figure 4. For example, suppose that a two wire cable has been checked; it will then be desired that when relay 4| steps to number 3 posit-ion that relay E will become energized and the system will recycle to home position. In these circumstances, referring to Figure 4, the cable selector switch '|3 will be set to its contact 16 which connects to the third contact of the contact panel J4 as shown. The circuit venergizing relay E will be from winding 6| through wire |05, through the winding of relay E, wire I I9 to contact 42 of panel JI, contact 42 of panel J3 (Fig. 4) wire |20, selector switch '|3, contact 16, wire |2I, contact 3 of panel J4, contact 3 of panel J2, wire |22, blade 3K2 and contact 3103 of 3K relay which will be energized at this time, wire 9| blade G2, through the contact g4 of relay G and wire |39 back to the winding 6|. When relay El energizes it completes a locking circuit for itself through its contact el and contact bl of relay B. Contact e2 of relay E completes a circuit connecting the winding 43 of relay 4| to the transformer winding 62, this circuit being as followsz from winding B2 through wire 85, wire 98, contact b2 of relay B, wir'eI25, contact 45 of relay 4 I, blade'44, wire |26, contact e2of relay E, blade E2, wireY |14-, contact a3`of relay A, blade A2, wire 81, winding '43; wire (Stand.` the rectifier. tubes back to winding 62.

This circuit causesl the relay 41| to beself-stepping under control of contacts' 45 and 44 until 1 it reaches home position'y at which .position relay: B becomes' energized through the contact Hof relay 4| and this openscontact b2 which de-energizes the relay E. De-energization of relay E, of course, removes power from the winding 43 ofr relay 4| and the locking circuit of relay E' will be open also at this time. The system is now-in an inactive position and is prepared to have another cable plugged into the adaptor for testing. Contact e3 of relay E serves to energize the relay' F when relay E is energized, and this opens contact fl of relay F, which cuts off power from relays IK, 2K and so on to prevent .energizationof these relays when the relay 4| is returningto home position.

For convenience,A a review ofv the apparatus will now be given. Assume a multi-conductor cableto be connectedbetween J I and J2, with the individual conductors of the .cable connected between correspondingly number terminals 'of JI and J2. This operatively connects a conductor between blades KI and K2 of each of the Wire selector relays, the number of wire selector -relays connected being dependent upon the number of wires in the particular cable to be tested.- All wire selector relays are generally at rest in they normally de-energized relationship shown. In this relationship the blades KI and K2 connect the corresponding conductor to the common ground bus, through back contacts k2 and 194 and isolating resistors 99 and |02, respectively. The resistors 99 and |02 are of. such low value as to be insignificant compared with the insulationresistance being tested; therefore, for. insulation test purposes both ends of all cable conductors being tested are electvely connected to ground bus |09.

All contacts 79| of each wire selector relayv are connected with test bus or wire 92 and all contacts k3 of all wire selector relays are connected with test bus or wire 9|.

Test buses or wires 9| and 93 connect to blades G2 and GI of test change-over relay G. This relay G in de-energized position connects test buses or wires 9| and 9'2 to the continuity detector circuit through back contacts g4 and g2, respectively. When relay G is energized it connects test buses 9| and 92 to the insulation test circuit through blades G2, GI, and front contacts g3 and gl, respectively, and conductor |00.

To test any particular conductor of the specimen cable, its corresponding wire selector relay is energized, thereby connecting the particular conductor to be tested between test buses `9| and 92, and disconnecting it from ground. These test buses are connected rst to the continuity detector circuit for a period of time, at the end of which they are connected to the insulation test circuit for a period of time. This transfer is effected by energizing relay Gfor the desired time y by cam 50 actuating switch 53.

Sequential energization of the wire selector relays of Fig. 3 is effected by means of the stepping relay 4| the stepping of which is in turn periodically controlled by the cam 52 actuating switch 55.

The insulation test'circuit may comprise the suitable voltage supply means 61 and a fault current detector, for example, relay M, for eventual application between the test buses 9|, 92 and ground.

1n the event of an insulation fault, current will flow from the voltage supply 61 throughV the contacts of change-over relay G when energized, to' test buses 9|v and/ or. 92' through" contacts 'lcIz and/oreki of the venergized wire selector relay associated with the particular conductor under tests, through the conductor under tests, through its insulation fault, to ground in the event of a direct ground fault, or, in the case of a cross faultV to other conductors of the specimen cable through that fault, through associated resistors 99 and/or |02 to ground and thence through the fault current detector (relay M as shown herein) back to thel voltage supply 6l.

'The continuity test circuit may comprise a suitable voltage supply (for example, secondary winding5| of transformer 59), wire |30, contact g4, blade G2 of relay G in its de-energized condition, to test bus or wire 9|, contact k3, blade K2 of the venergized wire selector relay associated with the particular conductor under tests, thence through the connector J2 to the particular conductor under tests, through connector J to the blade KI, to contact kl of the energized wire selector relay associated with the conductor under tests, to the test bus or wire 92, blade GI, contact g2 of the de-energized relay G, to the continuity fault detector shown in Fig. 2 as relay C and sensitivity adjusting control ID3-|06, wire |04 and wire |05 back to the voltage supply (secondary winding 6| of transformer 59) From the foregoing those skilled in the art will observe that we have provided a system and arrangement whereby cables having multiple wires may be plugged into the system and very quickly tested for insulation resistance and continuity merely by pressing the start button of the instrument. The instrument makes it possible to test a'large number of cables in a very short time without danger of overlooking any particular wire. The system provides for the necessary interruptions and indications in the event that a fault is discovered by the instrument in any individual wire.

The foregoing disclosure is representative of a preferred form of the invention and it is to be understood that various modifications, alterations and variations may be made by those skilled in the art without departing from the spirit and scope of the invention and it is accordingly intended that the boundaries of the invention shall be determined by the scope of the claims appended hereto.

I claim:

l. In an automatic test system for testing each of a plurality of wires in a cable comprising, in combination, means comprising a plurality of double pole double throw relays having their movable contacts connected to corresponding receptacles into which adaptors at the ends of the said cable may be plugged, one adjacent pair of each of said relay contacts being connected to a common bus and the other pair of adjacent contacts being connected to the movable contacts of a double pole double throw change-over relay, one pair of adjacent contacts of the change-over relay being connected in series with a source of relatively low voltage and the other pair of adjacent contacts of the change-over relay being connected together and to one terminal of a high voltage source, the other terminal of the high voltage source being connected to the aforesaid common bus, means including a timing device and switches operated thereby for connecting the said other pair of adjacent contacts of the changeover relay to the movablecontacts of each of the first mentioned double pole double throw relays for a time interval during which the change-over relay is thrown from one position to its alternate position whereby each wire of the cable is 10 checked for both continuity and insulation in-` tegrity. i

2. The structure of claim l including a lock-out relay having an actuating coil in series with the high Voltage source to disconnect at least one timing device switch to interrupt the testing procedure in the event of a fault in the wire. and a second relay having contacts in series withsaid at least one timing device switch, these contacts being normally open, and an actuating coil connected in series with the source of low voltage whereby insufficientl current through the cable during the continuity test likewise interrupts the testing procedure.`

s. Apparatus for testing each conductor of a inulticonductor cable for electrical continuity and electrical isolation from other conductors comprising a, first and a second receptacle each having an equal number of corresponding .terminals, each pair of corresponding terminals being adapted to be connected in series with a conductor of said cable, a rst two-pole double throw switch, hereinafter Itermed the wire selector switch, for each pair of corresponding4 terminals and having the movablecontacts connected'respectively to each pair of terminals, a ii'rst pair or' adjacent switch contacts each connected respectively through a resistor to a common bus, and Vthe other pair of adjacent switch contacts being connected to the movable contacts of a second double pole double throw switch, hereinafter termed the change-over switch, a source of high potential having one pole thereof connected to the common bus through a first alarm relay actuating coil and the other pole'of said source of high potential being connected to a first .two adjacent stationary contacts of said change-over switch, the second pair of adjacent contacts of the change-over switch being serially connected through the actuating coil of a second alarm relay to a source of low voltage electric current, said change-over switch second pair of adjacent contacts being normally engaged with the change-over switch movable contacts and the movable contacts of the wire-selector switch being normally in contact with the first pair of adjacent wire-selector contacts thereby normally connecting both ends of each cable conductor to the common bus, whereby under the condition of the wire-selector switch movable contacts being connected to the second pair of wire-selector switch stationary contacts, the source of low voltage electric current is connected in series with the second alarm actuating coil and the corresponding cable conductor to check the cable conductor for continuity; and when the changeover and wire-selector switches are thrown Ito their alternate pairs of contacts, a, high voltage is impressed through the rst alarm actuating coil on both ends of the corresponding conductor, all the other pairs of terminals remaining connected to the common bus to thereby check the cable conductor for insulation integrity.

4. The apparatus of claim 3 wherein each of said wire-selector switches includes an actuator coil, each of said actuator coils being connected in series with a corresponding switch point of a stepping switch, whereby the position of the stepping switch selectively inserts a corresponding conductor in the test circuit.

5. The apparatus of claim 4 in which said stepping switch has a spring actuator for advancing it one step at a time, an actuator coil for cooking said spring actuator, a, pair of normally closed contacts with an armature for one of the contacts in. proximity to. said actuator coil; aA timing motor, a first cam having a, recess and mechanically coupled to said .timing motor, a first cam switch hereinafter termed the cam synchronizing switch, having a cani follower riding on V.said first cam and being .electrically closed legicept when the cam follower is in the cam recess, a starting re1ay having a triplepole switch andan actuator coil, a manual switch, Said, cam Synchronizing switch having one contact connected to a. rst side of .a voltage source., and the other Contact connected to. anrst movable Contact of saidstarting relay. thestarting contact associated with said rst movable Contact ci thesjarting relay being connected to one end of the starting relay actuator coil and to one contact of the manual switch, the other contact of thevmanual switch being connected to the said first side of a voltage source, andthe other end of the starting relay actuator coil `being connected to the other side of the said voltage source, ,a second cam coupled .to ,said timing motor and having a lobe angularly displaced from the iirst cam recess, a second .cam switch operatively related to the second cam, the second movable contact of the starting relay breingdouble throw thereby having alternate rst and second contacts with the second 4contact in rcontinuity with the second movable contact when the starting actuator coil is not energized, asource of stepping relay actuator coil energizing potential connected in series with the stepping relay :actuator coil and the second cam switch second contact whereby when the manual switch is momentarily closed the starting relay first switch ris closed thereby starting a cycle by angularmovement oftthe'first cam closing-the synchronizing camiswitchttlieroby shunting the-manual switch and uponl rotation of the timing motor through a portion of va revolution the second cam switch closes thereby energizing the stepping switch actuator coil to cock the stepping switch spring, and upon further rotation of the timing motor the second cam switch opens thereby deactivating the stepping switch actuator coil to permit the spring tomove the stepping switch through one position, yand substantially simultaneously the first camgswitch opens to deenergize the starting switch relay.

6. The .apparatus of claim 5 including a third cam and third cam switch and circuit means including a source of potentiaLand said thirdfcam switch connected to-the change-over switch actuator coil to cyclically throwrthe changeeover switch from the rst position to thesecond `position to automatically check both resistance and insulation integrity.

LOUIS J. KABELL. RICHARD A. RICHARDS.. ALLEN L. DYER.

REFERENCES CITED The following references are of Arecordin the file of this patent: 

